Type bar anti-rebound mechanism



Feb. 17, 1970 w. J. Moss TYPE BAR ANTI-REBOUND MECHANISM Filed March '7, 1968 INVENTOR ms ATTORNEYS United States Patent Ofice Patented Feb. 17, 1970 3,495,529 TYPE BAR ANTI-REBOUND MECHANISM Wendell J. Moss, Horseheads, N.Y., assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Filed Mar. 7, 1968, Ser. No. 711,244 Int. Cl. B41j 9/00, 9/42 US. Cl. 101-93 7 Claims ABSTRACT OF THE DISCLOSURE An anti-rebound device on a print hammer contactable with a type bar as used in business equipment, the device including a captured ring element freely movable for absorbing energy to prevent rebound of the type bar. The print hammer carries a headed stud entrapping the ring element, which is positionable to either of two positions on the stud in response to fore-and-aft movement of the type bar.

BACKGROUND OF THE INVENTION Various mechanisms and devices have been heretofore employed for preventing shadow or ghost printing, which printing is caused by repeated movement of the printing hammer and/or of the type carrier. While most of these mechanisms and devices, such as weights and counter-weights, spring-loaded elements, arresting pawls, etc., have been successful in their particular application, the present trend to higher printing speeds is seen to impose some limitations on the use of many such devices, as their reaction time is considered too slow. Additionally, as the speed of printing increases, another factor which must be considered is the higher noise level in printer operation at the faster speeds. It is therefore desirable to provide a device which both reduces printer operation noise level and at the same time prevents print producing rebound impressions, so as to insure a clear and distinct print on the paper or other record material employed.

SUMMARY OF THE INVENTION This invention relates generally to improvements in means for preventing rebound of the print producing type elements commonly used in business equipment, such as cash registers and calculating and like computing machines. More particularly, the invent-ion relates to an improved anti-rebound mechanism adapted to hammer-actuated type bars or levers of the kind used in printers of the type shown and described in US. Letters Patent No. 2,905,382, issued to Guido Carnacina on Sept. 22, 1959.

In such a printer constructed according to the Carnacina patent, the essential portion of which is further illustrated and described herein, and in so far as it relates to the present invention, the type bar or lever employed is pivotally connected to the machine differential mechanism and, upon being set therethrough to a precise digit-recording position with respect to a platen-supported record material, is itself struck by an associated hammer member under force of a powerful spring and thereby driven against the platen with a sudden blow. With such construction, it has been found that when the hammer member completes its full printing stroke, it tends to rebound from the type bar or lever and, under the action of the driving spring, returns to strike the type bar or lever a second time with sufficient force to cause in some instances a second impression, this being the shadow or ghost impression, to be made on the record material.

A partial remedy to such shadow printing due to the hammer member striking the type bar or lever a second time has been found to exist when the hammer member, while so providing the striking force needed for effecting an impression from the type bar on the record material, itself engages a fixed stop and hence completes an actuating stroke short of following the type bar to printing engagement against the platen. In this respect, the hammer propels the type bar through the space and against the platen; however, the hammer itself does not travel the full distance or follow the type bar to the printing position. Thus, the positions of the type bar and of the hammer at the completion of the printing stroke reduce the possibility of the rebounding or repeated striking of the type bar against the platen. In other words, the hammer is held in a position spaced from the type bar, so that the heavy actuating spring for the hammer does not allow the hammer to repeatedly bounce the type bar against the platen.

The present invention provides a device connected with the printing hammer whereby the overall printer noise level is reduced by virtue of its construction and movement, and wherein the printer type bar does not rebound in its operation after being struck by the hammer. The device includes a loosely-held ring member which is in one position on a stud when the hammer is engageable with and is ready to propel the type bar, and which is in another position when the type bar has moved away from the hammer after being propelled, and which returns to the first-mentioned position as the type bar is moved to its original, or normal, condition, in engagement with the hammer. In the first-mentioned position of the ring member, when the print hammer is in a cocked, or ready-forfiring, condition, the ring is disposed approximately horizontal in relation to the stud, and when the hammer has propelled the type bar to the printing condition, the ring is disposed approximately vertical in relation to the stud.

With the above discussion in mind, it is seen that the principal object of the present invention is to provide an anti-rebound device for a printing mechanism, so that the type bar does not repeat in its print producing operation.

A further object of the invention is to provide an antirebound device so arranged as to present a printer unit substantially less noisy in the regular operation.

An additional object of the invention is to provide an anti-rebound device on the hammer which eliminates rebounding of the type bar against the platen.

A still further object of the invention is to provide an anti-rebound device on the hammer which is spaced from the type bar at the moment of the printing, so as to allow the type bar to freely return to engagement with the hammer.

Many other features and advantages of the present invention will become clear and fully understood from a reading of the following description taken together with the annexed drawing, in which:

FIG. 1 is a side elevational view of a printer unit of the spring-actuated hammer type embodying the present invention, the hammer and the type bar being in position for making a printing stroke;

FIG. 2 is a view taken on the line 22 of FIG. 1;

FIG. 3 is a side elevational view showing the positions of the hammer and the type bar upon taking a printing stroke; and

FIG. 4 is a similar view showing the positions of the hammer and the type bar just after the printing stroke.

Although only one printer unit will be described herein, it should be understood that a plurality of such printer units may be provided in side-by-side relationship to correctly and adequately print the desired characters. Also, as the above-cited Carnacina US. patent shows and describes a complete printer assembly along with the associated drive mechanism forming a part of the business machine, to which patent reference may be had, the present disclosure will be confided to the showing of mechanism of the Carnacina machine essential to a full understanding of the present invention.

Referring to FIG. 1, there is shown a cross shaft 10, which, under control of a suitable driving means such as an electric motor or the like, is rocked first clockwise and then counter-clockwise in the printing operation. Although not illustrated, the cross shaft would normally be journalled in vertical side plates of the machine printer framework construction. Secured to the shaft 10 and ex tending rearwardly therefrom, or toward the left in FIG. 1, is a drive arm 12 having a roller 14 riding in a lower cam slot 16 of a lever 18 rockably supported as at 20.

In the manner fully described in the above-cited Carnacina US. patent, a differential sector plate 22, pivoted on a cross shaft 24, is actuated at a precise time during machine operation for differential setting by a selected pin in an associated pin carriage. Such pin carriage is also adequately shown and described in the above-cited Camacina US. patent and hence will not be further described, except to say that the differential setting of the sector plate 22 takes place upon the lip portion 25 thereof coming into stopping engagement with an aligned pin of the carriage. As illustrated (FIG. 1), the sector plate 22 includes a rear arm portion 26 pivotally connected at the pin 28 with the lower end portion 31 of an upstanding type bar 30, which type bar has, spaced along its upper rear edge, a raised type area 32 representing digital characters. With such construction, as the sector plate 22 is rotated about the shaft 24, the type bar is raised or lowered an amount corresponding to the digit amount set up on the machine keyboard for entry into the machine.

Mounted rearwardly of the type bar 30 is the usual platen 34, which carries the paper or other record material on which the digits or characters are printed by reason of the type bars being forcibly moved thereagainst by an associated hammer 36. A guide comb 38, suitably supported, maintains the upper end of the type bar in proper alignment, and a spring 40, extending between the type bar lower end portion 31 and the sector plate arm portion 26, is effective to hold the type bar normally forwardly and fully within the comb 38, as seen in FIG. 1.

Pivotally supported rearwardly of the sector plate 22, as on a cross shaft 44, is a bell crank lever 46 having a forwardly-extending arm portion 48 engageable by means of a turned-over car 50 with a protruding finger 52 of the sector plate arm portion 26. Positioned upwardly of the lever 46 and rearwardly of the type bar type area 32 is a hammer latch member 54 pivotally carried on a further cross shaft 56, the latch member 54 having a rearwardlyextending arm portion 58 pivotally connected as at 60 to a downwardly extending hammer trip leg 62. A spring 64 tensioned between the printer framework (not shown) and the leg 62 maintains said leg normally clockwise and, by means of an appropriate coupling 68 slidingly interconnecting the lower end of the leg 62 and the upper end of the bell crank lever 46, likewise maintains said lever normally counter-clockwise, with its ear portion 50 in abutment with the under surface of the sector plate finger 52.

As illustrated (FIGS. 1, 3 and 4), the lever 18 is provided with a rearwardly-extending arm portion 70 carrying a hammer trip bar 72, which is engageable with a lower shoulder 74 on the leg 62. The arm portion 70 also carries a restoring ball 76 engageable with the lower rear edge 77 of the hammer 36. The latch member 54 carries on its lower end a hooked ear 78 engageable with a trip lug 80 on the hammer 36, which lug 80 is adjacent to the 4 hammer lower edge 77 and is a part of a hammer rear end portion 81. A hammer stop bar 96 is supported between the printer framework and is so positioned as to be engaged by the lug 80 upon firing of the hammer member from its retracted, or cocked, position.

The anti-rebound device making up the present invention is associated with and is carried by the hammer 36, which is continuously biased in a counter-clockwise direction by means of a strong spring 82 acting also to maintain the hammer rotatably captured about a support rod 84. A stop bar 86 provides a limit to clockwise rocking of the hammer toward its retracted position, as such hammer is so positioned in FIG. 1. As illustrated, the anti-rebound device includes a headed stud 88 secured to the upper portion of the hammer 36 (FIG. 2) and a ring member 90 entrapped on the stud (see also FIG. 1). The overall dimensions of the ring member 90 include an internal diameter which is substantially larger than the diameter of the body of the stud 88 but which is slightly smaller than the diameter of the head 88a of the stud 88 (FIG. 2), so that the ring 90 is actually captured between the stud head 88a and the hammer 36. The width of the ring is such that it is loose or free to rotate or roll on the stud. Thus it is moved or Wobbled from one position to another position and back to its original position. As illustrated, the ring assumes an eccentric position in relation to the center line of the stud 88 as it performs its function. The ring width is also such that, due to the location of the hammer 36, the ring alone is engaged or available for engagement with the hammer-associated type bar 30 (FIG. 2). As seen from the illustrations of FIGS. 1, 3, and 4, and as now to be described, the anti-rebound feature is obtained by moving the ring 90 about the stud 88 from one position to another position approximately ninety degrees from the first position.

Referring to FIG. 1, where the type bar 30 is in its non-printing, or retracted, position and, under urgence of the spring 40, is biased toward the cocked hammer 36, the ring member 90, in being then pressed against by the type bar, is in a normally forward or home position substantially horizontal with respect to the stud 88. This type bar positioning of the ring 90 is maintained until the printer unit is called upon for actuation during a machine operation.

According to the above-cited Carnacina U.S. patent, the printing unit is released to drive the type bar 30 into engagement with the platen 34 at a precise point in cycling time following the entry of digital data into the machine through actuation of the different sector plate 22. In this regard, as the plate 22 is rocked clockwise about the shaft 24, the type bar 30 is moved upwardly the corresponding distance for aligning the keyboard-selected digit with the platen 34 by reason of the arm portion 26 being connected at the pin 28 to the lower end portion 31 of the type bar. As the sector plate finger 52 moves upwardly and away from the lever ear 50, clockwise rocking of the leg 62 takes place immediately under urgence of the spring 64 and continues until the interconnected bell crank lever 46 rocks that extent counter-clockwise to abut against the associated stop bar 47 (FIG. 1). As understood from FIG. 3, this rocking of the leg 62 is sufficient to present its lower shoulder 74 in operating alignment with the lever-18-carried trip bar 72.

Upon regular rocking of the cross shaft 10 during a machine operation, first clockwis'e, the roller 14 moves upwardly within the slot 16 and rotates the lever 18 counter-clockwise. When this happens, the trip bar 72 moves downwardly against the shoulder 74 of the leg 62 and thereby rocks the interconnected latch member 54 counterclockwise against the bias of the spring 64, in turn disengaging its hooked car 78 from under the lug 80 and releasing the hammer 36 for counter-clockwise drive under action of its spring 82. This, of course, propels the type bar 30 into engagement with the platen 34 (FIG. 3). The hammer itself does not follow the type bar 30 to the platen 34 but is limited in its travel by the stop bar 96 suitably secured to the machine frame. That is, as seen in FIG. 3, after the ear 78 has been released from the lug 80, the lug 80 moves downwardly and against the stop bar 96, and the hammer is thereby prevented from following the type bar in its engagement with the platen. As also seen in FIG. 3, counter-clockwisemovement of the lever 18 has moved the restoring ball 76 away from the lower edge 77 of the hammer 36, andsaid hammer has likewise moved from engagement with its cocking position stop bar 86. It is also seen that, at such time of hammer firing position, the ring 90 has rolled or otherwise moved gravitationally from its contact position with the type bar 30 to a freely hanging position on the stud 88. In this respect, it is understood that the ring 90 has moved from a substantially horizontal position prior to hammer firing (FIG. 1) to a substantially vertical position after hammer firing (FIG. 3).

In FIG. 4, the type bar 30 is illustrated after it has retracted from engagement with the platen and again is in engagement with the ring 90, which is now rolled or rocked on the stud 88 back to its original position. The ring memher or energy-absorbing element 90 shifts or swings automatically from a first, or normal, position to a second position, and then moves back to the first position during the printing cycle of machine operation. Rebound of the type bar 39 against the platen 34is thus effectively prevented, as the return contact of the type bar with the hanging ring (vertical) and subsequent rolling movement of the ring bythe type bar back to normal (horizontal) absorbs the full extent of any energy then built up and hence available in such type bar, which heretofore caused bouncing or repeating engagement with the platen.

As mentioned earlier, the instant anti-rebound device also lowers the operational noise level which is commonly a problem in case of metal-to-metal contact in high-speed printing operations. Noise is greatly eliminated by virtue of the position of the hammer 36 in relation to the type bar 30 during the actual printing, and also of the fact that the ring 90 is rolled or rocked from the vertical posi tion of FIG. 3 to the horizontal position of FIG. 4.

Restoring of the hammer 36 and the type bar 30 to their retracted, or cocked, positions takes place in regular order during machine operation as the cross shaft is returned counter-clockwise and back to home. This returns the lever 18 clockwise from its position of FIG. 3 to its position of FIG. 1, where its restoring bail 76 re-eng' gages the lower rear edge 77 of the print hammer 36 and returns it sufiiciently clockwise to permit relatching of the hammer lug 80 by the hooked ear 78 of the latch member 54. The spring 40, of course, causes the type bar to maintain engagement with the ring member and follow the hammer as such time. In a like manner, the regular returning of the sector plate 22 counter-clockwise and back to home during machine cycling, and also through the action of the spring 64, effects restoring of the coupled members 46 and 62 back to their starting positions, as shown in FIG. 1.

It is thus seen that herein shown and described is an anti-rebound device for a printing mechanism which accomplishes all the features and advantages of quite and positive operation of the type bar and hammer. The particular construction and operation of the ring on the hammer dampen the action of the type bar by rolling the ring on the supporting stud as the bar moves from the printing position to the retracted position. While only one embodiment has been shown and described, variations on this device may of course occur to those skilled in the art. It is thus contemplated that all such variations are within the scope of the present invention, and the invention is not to be taken as limited in any manner except as defined in the following claims.

What is claimed is:

1. In a printing mechanism having a platen, a type bar, a hammer for driving the type bar into printing engagement with the platen, and means for preventing rebound of the type bar onto the platen after initial contact therewith, said rebound-preventing means comprising a stud secured to the hammer, and a ring member loosely carried on the stud and entrapped thereby, the ring member being aligned with the type bar and engageable therewith in one position when the type bar is at a platen-nonengaging position, the member being shiftable automatically to another position upon disengagement of the type bar therefrom when driven by the hammer into platen engagement, and being shiftable back to said one position upon re-engagement by the type bar therewith when returning to the platen-non-engaging position.

2. In a printing mechanism in accordance with claim 1 wherein said ring member is aligned in an approximately horizontal position with respect to said stud upon engagement by said type bar when at its platen-non-engaging position, gravitationally rollable to an approximately vertical position with respect to said stud upon engagement of said type bar with said platen, and rollable back to the approximately horizontal position with respect to said stud upon re-engagement by said type bar when returning to its platen-non-engaging position.

3. In a printing mechanism in accordance with claim 1 wherein said ring member is aligned in an approximately horizontal position with respect to the stud upon engagement by the type bar when at its platen-non-engaging position, gravitationally swingable to an approximately vertical position with respect to the stud upon engagement of the type bar with said platen, and swingable back to the approximately horizontal position with respect to the stud upon re-engagement by the type bar when returning to its platen-non-engaging position.

4. In a printing mechanism in accordance with claim 1 wherein said ring member is freely hanging on said stud in the platen-engaging position of the type bar.

5. The combination of a platen member, a type carrier adjacent said platen member, an impression hammer normally engaging said type carrier, means operating said impression hammer from a non-printing condition to a printing condition where said type carrier is driven thereby against said platen member, and dampening means positioned between said type carrier and said impression hammer for preventing the type carrier from rebounding against the platen member during each operation of said impression hammer, said dampening means comprising an annular member on said impression hammer normally urged to a first position upon engagement by said type carrier when said impression hammer is in its non-printing condition, said annular member falling gravitationally to a second position upon said impression hammer reaching its printing condition, and said annular member returning to the first position upon re-engagement by said type carrier with said impression hammer at its non-printing condition.

6. The combination of a platen member, a pivotable type carrier positioned adjacent said platen member, an impression hammer normally engaging said type carrier, means operating said impression hammer from a retracted position to a printing position where said type carrier is driven therefrom and against said platen member, and means for restraining movement of said type carrier comprising a ring member on said impression hammer engageable by and operably associated with said type carrier for preventing the type carrier from reboundagainst the platen member during each operation of said impression hammer, said ring member being normally urged to a first position upon engagement by said type carrier when said impression hammer is in its retracted position, said ring member falling by gravitational force to a second position upon said type carrier leaving said hammer upon reaching its printing position, and said ring member being returned to its first position upon re-engagement by said type carrier upon return from said platen member.

7 8 7. The combination of claim 6 in which said restrain- 2,117,451 5/1938 Robertson 10193 ing means comprises a stud secured to the hammer and 2,204,187 6/1940 Ostler 101--287 X extending laterally therefrom, the ring member being 2,307,669 1/1943 Crosman 10.194 loosely captured on the stud. 2,353,057 7/1944 Mills 10193 2,616,366 11/1952 Eickman 101-93 References Cited 2,625,100 1/ 1953 Williams et a1. 10193 UNITED STATES PATENTS 2,696,782 12/1954 JOhHSOn 101-93 1,508,532 9/1924 Quentell 101-94 11 22; $1322 $3 1,652,057 12/1927 Shipley 10196 1,908,140 5/1933 Going 197 25 10 WILLIAM B. PENN, Primary Examiner 

